Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2001-07-26
2002-09-24
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090150
Reexamination Certificate
active
06453858
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a device for varying valve timing of gas exchange valve of an internal combustion engine, particularly a hydraulic camshaft adjusting device of a rotary piston type comprising:
a drive pinion connected in driving relationship to a crankshaft of the internal combustion engine and a winged wheel connected rotationally fast to a camshaft of the internal combustion engine,
said drive pinion comprising a hollow space formed by a hollow cylindrical circumferential wall and two side walls, at least one hydraulic working chamber being formed in the hollow space by at least two radial limiting walls,
at least one wing arranged on an outer periphery of a wheel hub of the winged wheel extending radially into the at least one working chamber and dividing this working chamber into two oppositely acting hydraulic pressure chambers,
by a selective or simultaneous pressurizing by a hydraulic pressure medium, the pressure chambers effect a pivoting or a fixing of the winged wheel relative to the drive pinion, and thus, of the camshaft relative to the crankshaft,
on switching-off of the internal combustion engine, an auxiliary energy acting between the winged wheel and the drive pinion rotates the camshaft into a preferred basic position for starting the internal combustion engine,
in the basic position of the camshaft, the winged wheel can be mechanically coupled to the drive pinion by a lock that can be hydraulically unlocked again upon renewed pressurizing of the device.
BACKGROUND OF THE INVENTION
A generic device of the pre-cited type is known from DE 198 44 473 A1. This device configured as a so-called vane-type adjusting device essentially comprises a drive pinion connected in driving relationship to a crankshaft of the internal combustion engine and a winged wheel connected rotationally fast to a camshaft of the internal combustion engine. The drive pinion comprises a hollow space formed by a hollow cylindrical circumferential wall and two side walls, four hydraulic working chambers being formed in this hollow space by four radial limiting walls. On the periphery of its wheel hub, the winged wheel correspondingly comprises four wings each of which extends radially into one of the working chambers of the drive pinion and divides the working chamber into two oppositely acting hydraulic pressure chambers. When selectively or simultaneously pressurized by a hydraulic pressure medium, these pressure chambers effect a pivoting or a fixing respectively, of the winged wheel relative to the drive pinion, and thus, of the camshaft relative to the crankshaft. When the internal combustion engine is switched off, an auxiliary energy acting between the winged wheel and the drive pinion rotates the camshaft into a preferred basic position for starting the internal combustion engine, in which position, the winged wheel can be mechanically coupled to the drive pinion by a lock. The lock of this device is a spring-loaded locking pin that is movably arranged in a radial bore of a limiting wall of the drive pinion and that, in the basic position of the camshaft, snaps into a radial reception bore arranged in the wheel hub of the winged wheel between two wings. The reception bore is in hydraulic communication with the pressure medium supply to those pressure chambers that have a minimized volume in the basic position of the camshaft so that, due to the pressure loading of these pressure chambers at a re-starting of the internal combustion engine, the locked locking pin is pushed against the action of its spring load into the radial bore in the limiting wall and is thus hydraulically unlocked again.
Another possibility of mechanically coupling the winged wheel to the drive pinion of a camshaft adjusting device of a rotary piston type is known from the device disclosed in DE-OS 196 23 818. The structure of this device configured as a so-called pivoting wing adjuster corresponds basically to that of the vane-type adjuster described above except that the wings of its winged wheel are more massive and that it generally comprises only two to three hydraulic working chambers. The mechanical coupling of the winged wheel to the drive pinion is effected in this device by a likewise spring-loaded locking pin that is slidably arranged in an axial bore in a wing of the winged wheel and that, in the basic position of the camshaft, snaps into an axial reception bore in one of the side walls of the drive pinion. Similar to the previously described device, this reception bore communicates with the pressure medium supply of the hydraulic pressure chambers of the device acting in one direction so that, when these pressure chambers are pressurized, the locked locking pin is hydraulically unlocked again in a similar manner and is pushed into the axial bore in the wing of the winged wheel.
These locks in the form of a radial locking pin and an axial locking pin for coupling the winged wheel and the drive pinion of a camshaft adjusting device of a rotary piston type, however, have the drawback of being comprised of a plurality of additional, separate parts and additional pressure medium ducts and reception bores that unfavorably increase the fabrication and assembly costs and, thus, the overall manufacturing costs of such a device. A further drawback of such locks is that the end face of the locking pin usable as a pressure application surface for unlocking is relatively small so that a pressure medium pressure sufficient for unlocking takes a relatively long time to build up and thus prolongs the unlocking time of the device. Moreover, in these devices, the basic danger exists that the pressure medium pressure desired in the pressure chambers in communication with the locking pin is built up earlier in the pressure chambers themselves than on the pin and thus produces a bracing torque between the winged wheel and the drive pinion which causes a clamping of the locking pin in its locking position so that an adjustment of the device is rendered impossible.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a device for varying the valve timing of gas exchange valves of an internal combustion engine, and more particularly to provide a hydraulic camshaft adjusting device of a rotary piston type in which the winged wheel and the drive pinion can be coupled mechanically to each other by a lock, the device being distinguished by the small number of its individual parts and by low fabrication and assembly costs while being configured with a pressure application surface that is large enough to assure a quick hydraulic unlocking.
This and other objects and advantages of the invention will obvious from the following detailed description.
SUMMARY OF THE INVENTION
The invention achieves the above objects by the fact that the lock for mechanically coupling the winged wheel to the drive pinion is formed by at least one cage-guided free-wheel that is arranged between the winged wheel and the drive pinion and comprises at least one clamping body that blocks the direction of rotation of the winged wheel opposed to the basic position of the camshaft, at least parts of the surface of the cage of the free-wheel being configured as a pressure application surface for the hydraulic pressure medium for a hydraulic unlocking of the free-wheel.
In a particularly preferred embodiment of the invention, it has proved to be sufficient if the lock of the device comprises only one free-wheel made according to the invention and only one clamping body is guided by its cage because this reduces the fabrication and assembly costs of the lock to a minimum. For a further reduction of costs for the lock of the device, advantageously, the clamping body of the free-wheel is configured as a simple rolling bearing needle roller and the cage of the free-wheel is made of a heat-resistant plastic. However, the invention also includes solutions in which the free-wheel comprises a plurality of clamping bodies, for example, two or more rolling bearing balls arranged next to one another and/or in which the cage is
Haag Michael
Scheidt Martin
Strauss Andreas
Bierman, Muserlian and Lucas
Denion Thomas
INA Walzlager Schaeffler oHG
O'Brien Sean
LandOfFree
Device for varying valve timing of gas exchange valves of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for varying valve timing of gas exchange valves of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for varying valve timing of gas exchange valves of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2821045