Device to change the timing of gas exchange valves in an internal combustion engine, in particular a rotating piston positioning device to adjust the angle that a camshaft is rotated relative to a crankshaft

#This invention pertains to a device to change the timing of gas exchange valves in an internal combustion engine, and it is particularly advantageous to implement in rotating piston positioning devices with a lightweight design that are used to adjust the angle that a camshaft is rotated relative to a crankshaft.

#A device to change the timing of gas exchange valves in an internal combustion engine is known from DE 196 23 818 A1, with this device defining a class and being designed as a rotating piston positioning device to adjust the angle that a camshaft is rotated relative to a crankshaft, with the device having a lightweight design, and being located at the drive end of a camshaft that is held in the cylinder head of the internal combustion engine. In principle, this device, also identified as a tilting-vane positioner, is designed as a hydraulic actuator that can be controlled in response to various operating parameters of the internal combustion engine, and is formed essentially of a drive member that is driven by a crankshaft of the internal combustion engine and a driven member that is fixed to the camshaft of the internal combustion engine. The drive member is made up of a drive pulley that contains at least two hydraulic working chambers formed within a hollow cylindrical lightweight metal stator with at least two intermediate radial walls, including two ferrous metal sidewalls. In contrast to this, the driven member in this device is provided in the form of a vane wheel formed in its entirety of a lightweight metal bolted axially to the camshaft by means of a central fastening screw. The vanes of this vane wheel extend radially into the working chambers of the drive pulley and divide each of the chambers into two opposing hydraulic pressure chambers. The drive member rotates external to the driven member, i.e. on the end of the camshaft and on the head of the central fastening screw. It transfers force to the driven member by means of the hydraulic pressure chambers formed within the device in such a way that by selectively or simultaneously charging these pressure chambers with a pressure medium, the driven member is rotated relative to, or fixed with respect to, the drive member. Consequently, the camshaft is rotated relative to the crankshaft.

#However, a disadvantage to this known device is that the driven member, which is made of a lightweight metal, must be bolted to the camshaft with a high torque from the central fastening screw so as to transfer the drive torque effected by the crankshaft of the internal combustion engine through the drive member to the driven member and effectively to the camshaft. However, in a driven member made of a lightweight metal or a plastic, high torques lead to detrimental compressive deformations and high stresses, mainly in the conical zone of force at the fastening screw, such that the driven member can only be bolted to the camshaft using low torques to avoid these compressive deformations and stresses. Thus, the driven member is only suitable for transferring small drive torques or chain forces to the camshaft. Transfer of higher drive torques or chain forces to the camshaft is only possible by increasing the friction between the driven member and the camshaft with the help of expensive coatings or surface treatments, or by using additional shape-locking elements at the contact surfaces, which are expensive as well. Even if the driven member is bolted with a higher torque to the camshaft so as to transfer high drive torques, the larger radial and axial play between the drive member and the driven member in the device, which are necessary due to the compressive deformations and the high stress, have the disadvantage that in addition to the increased danger of seizing, and thus the possibility of failure of the device, increased leakage of pressure medium occurs within the device that negatively influences the positioning speed and its ability to hold its angle. Moreover, a general disadvantage of the known device designed as a tilting-vane positioner is that the hole pattern for the pressure medium channels feeding the pressure chambers of the device, said pattern to be incorporated into the device's driven member, which for the most part is designed as a one-piece tilting vane wheel, is technically complicated to manufacture, relatively speaking. Also, it is relatively difficult to brace by hand against the torque applied to the fastening screw when installing the driven member onto the camshaft.

#This invention is explained in more detail below on the basis of the two preferred embodiment and is shown schematically in the associated drawings. In the drawings:

#FIG. 1 is a longitudinal cross-sectional view through a device according to the first preferred embodiment of the invention taken along line 1—1 in FIG. 2.

#FIG. 2 is a cross-sectional through the device according to the first preferred embodiment of the invention taken along line 2—2 in FIG. 1.

#FIGS. 1 and 2 and FIGS. 3 and 4 depict two different embodiments of a device 1 or 1′ to change the timing of gas exchange valves in an internal combustion engine, each of which is designed as a rotating piston positioning device to adjust the angle of rotation of a camshaft 4 or 4′ with respect to a crankshaft, which is not shown. Both devices 1, 1′ are located at the driven end 2, 2′ of the camshaft 4, 4′, which is held inside the cylinder head 3, 3′ of the internal combustion engine. Also, both devices are designed, in principle, as a hydraulic actuator that can be controlled in response to various operating parameters of the internal combustion engine. In particular, FIGS. 2 and 4 illustrate that the actual design of the devices 1, 1′ is in the form of a tilting-vane positioner that is formed essentially of a drive member 5, 5′ that is driven by the crankshaft of the internal combustion engine and of a driven member 10, 10′ that is fixed to the camshaft 4, 4′ of the internal combustion engine. In these devices 1, 1′, the drive member 5, 5′ is made up of a hollow cylindrical peripheral wall 6, 6′ and two side walls 7, 8 and 7′, 8′, respectively, each of which is made of a ferrous metal and the two of which when bolted together form a cavity that is subdivided into four sections by means of four intermediate walls 9, 9′ that extend radially inward from the peripheral wall 6, 6′. On the other hand, the driven member 10, 10′ of the devices 1, 1′ are formed as a vane wheel made of a lightweight metal. Four vanes 12, 12′ extend radially from its hub 11, 11′ into the sections formed in the drive member 5, 5′, subdividing each section into two hydraulic pressure chambers 14, 15 and 14′, 15′, respectively. Due to the lightweight design of the driven member 10, 10′, which is axially bolted to the camshaft 4, 4′ using a central fastening screw 13, 13′, the drive member 5, 5′ is supported radially external to the driven member 10, 10′ as it rotates, and force is transferred from it to the driven member through the hydraulic pressure chambers 14, 15 and 14′, 15′, respectively, that are formed inside the device 1, 1′. This force transfer is such that when the pressure chambers 14, 15 and 14′, 15′, respectively, are selectively or simultaneously charged with a hydraulic pressure medium, the driven member 10, 10′ makes a rotation relative to or is fixed with respect to the drive member 5, 5′. This causes the camshaft 4, 4′ to do likewise with respect to the crankshaft.

#Furthermore, as shown in particular in FIGS. 1 an 2 in both devices 1, 1′ according to this invention, the conical zone of force from the fastening screw 13, 13′ is transferred by a special collar 16, 16′ made of a compression-resistant material so as to prevent compressive deformations when the driven member 10, 10′, which is made of a lightweight metal, when it is fastened to the camshaft 4, 4′ using the central fastening screw 13, 13′. The driven member 10, 10′ is shape-locked and/or friction-locked onto this collar axially, radially and circumferentially, and an be bolted to the camshaft 4, 4′ without deforming. At the same time, the special collar 16, 16′ is designed as a prefabricated pressure medium distributor of the device 1, 1′, containing the majority of the pressure medium channels 17, 18 and 17′, 18′, respectively, that lead from the pressure medium feed and discharge ports of the device 1, 1′ to the pressure chambers 14, 15 and 14′, 15′, respectively, of the device. The collar 16, 16′ located in the driven member 10, 10′ is advantageously provide as a steel collar, whose exterior surface 19, 19′ serves at the same time as the external radial bearing for the side walls 7, 8 and 7′, 8′, respectively, of the driven member 5, 5′. In addition, the ends 20, 21 and 20′, 21′, respectively, of the collar 16, 16′ extended beyond the axial width of the device 1, 1′ and have on one side a means to brace against the torque applied to the fastening screw 13, 13′ and on the other side a means to center the device 1, 1′ on the camshaft 4, 4′.

#In the first embodiment of the device 1 according to the invention shown in FIGS. 1 and 2, the implementation of these features is accomplished by frictionally locking the driven member 10 onto the collar 16 radially and circumferentially by a press fit, while at the same time it is secured in the axial direction using shape-locking between a shoulder 22 on the collar 16 formed by an increase in its diameter and by a shoulder 23 on the end of the camshaft that sits against the side wall 8 of the drive member 5. It can also be seen from FIG. 1 that to design the collar 16 as a pressure medium distributor, two annular notches 24, 25 are made in the collar's exterior surface 19 that are connected to the pressure chambers 14, 15 of the device 1. One of these annular notches opens up into the center hole 30 of the collar 16 through radial holes, and the other opens into a number of axial notches 29 in the exterior surface 19 of the collar 16. There are two more annular notches 27, 28 on the exterior surface 26 of the camshaft 4 that are axially separated and that are connected to the pressure medium feed and discharge ports of the device 1. These annular notches are connected through a number of radial holes to the pressure medium channels 17, 18 in the collar 16 that are formed after the device 1 is installed on the camshaft 4 in such a way that annular notches 25 and 27 are hydraulically connected through radial notches 29 in the exterior surface 19 of the collar and annular notches 24 and 28 are hydraulically connected through the axial center hole of the collar 16. Moreover, in the embodiment shown in FIG. 1, the pressure medium feed and discharge ports of the device 1 are, for example, fed by a pressure medium console 38 connected to lubricant circuit 39 of the internal combustion engine, said console enclosing the annular notches 27, 28 in the exterior surface 26 of the camshaft 4. The steel seal rings located between the annular notches 27, 28 and at the camshaft shoulder 23, but not identified more closely, are intended to prevent internal and external pressure medium leakages when pressure medium is supplied to the device 1. Furthermore, as a means to brace against the torque applied to the fastening screw 13, FIG. 1 clearly shows that the end of the collar 16 opposite the camshaft is designed with a hexagonal head 31 on which to place an auxiliary tool. The end 21 of the collar 16 facing the camshaft is, on the other hand, itself designed as a means to center the device 1 onto the camshaft 4 by completely inserting it into a centering hole 32 in the rear 33 of the camshaft 4, the interior wall of the hole simultaneously sealing the axial notches 29 in the exterior surface 19 of the collar 16.