Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2002-07-24
2003-11-25
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090150, C123S090270, C123S090310, C464S160000
Reexamination Certificate
active
06651600
ABSTRACT:
This application is a 371 of PCT/EP00/11866 filed Nov. 28, 2000.
FIELD OF THE INVENTION
The invention concerns a rotary piston adjuster for adjusting the angular position of the camshaft of an internal combustion engine said adjuster comprising an outer rotor connected to a drive pinion and an inner rotor connected to the camshaft, the outer rotor comprising at least one hydraulic chamber having radial separating walls and the inner rotor comprising at least one pivoting vane that sealingly divides the hydraulic chamber into working chambers A and B and can pivot hydraulically between a retard stop position and an advance stop position, said adjuster further comprising a locking device suitable for detachably connecting the outer and the inner rotors.
BACKGROUND OF THE INVENTION
During the stopping and starting phases of an internal combustion engine, clattering noises are caused by the alternating torque of the camshaft when the rotary piston adjuster has been drained. To prevent these noises, the outer rotor and the inner rotor of the rotary piston adjuster are connected to each other in the start position which, in the case of a rotary piston adjuster of an inlet camshaft is the retard position and in the case of a rotary piston adjuster of an outlet camshaft, the advance position. In this way, besides a suppression of noise, a reliable engine start is also obtained.
There are numerous solutions for a reciprocal locking or latching of the outer and the inner rotor. The generic document DE 197 26 300 A1 discloses a rotary piston adjuster that is configured as a vane-type adjuster for adjusting the angular position of the camshaft of an internal combustion engine, said adjuster comprising an outer rotor connected to a drive pinion and an inner rotor connected to the camshaft. The outer rotor comprises at least one hydraulic chamber with radial separating walls, and the inner rotor comprises at least one pivoting vane that sealingly divides the hydraulic chamber into a working chamber A and a working chamber B while being hydraulically pivotable between a retard and an advance stop position. Further, a locking device for detachably connecting the inner and outer rotors is also provided.
This vane-type adjuster comprises in one of the vanes, an axially arranged, spring-loaded fixing pin whose conical tip is adapted to be introduced into a matching conical aperture in an end cover of the vane-type adjuster in one of the stop positions. Due to the slightly eccentric movement of the conical tip of the fixing pin into the conical opening, the pin has a wedge effect that results in a clearance-free locking of the outer and inner rotors. This latching and locking device operates reliably but is complex and prone to wear.
OBJECT OF THE INVENTION
The object of the invention is therefore to provide a reliably operating, inexpensive and durable locking device for a rotary piston adjuster of the pre-cited type.
SUMMARY OF THE INVENTION
The division of the rotary piston adjuster into the adjuster, as such, and the attachment comprising the locking device and the stops permits the use of an optimum material for the intended purpose in each case. Thus, for example, the not so highly loaded outer and inner rotors can be made of soft materials, like light metals or plastic, and the pointwise highly loaded components of the locking device and the stops can be made of wear-resistant materials such as hardened steel. The easy-to-work soft materials reduce the cost of construction and the wear-resistant materials reduce the space requirement, while the durability and the operational reliability of the rotary piston adjuster are enhanced.
A further advantage of the inventive solution is that the same type of attachment can be used with different types of rotary piston adjusters, and its modification is possible independently of the rotary piston adjuster.
The fact that the attachment at the same time forms the end closure of the outer rotor leads to a saving of axial design space. However, it is also conceivable to configure the drive pinion as an intermediate plate and arrange the locking device and the stops on the drive end while closing the end of the rotary piston adjuster directed away from the camshaft with a simple cover.
Advantageously, the locking device comprises a locking body configured as a flat slide that is guided in a guide groove of the intermediate plate that is connected to the outer rotor. Such a locking body requires only a small axial design space and is simple to make.
According to another advantageous feature of the invention, the disc-shaped bushing that is connected to the inner rotor is sealingly guided in a coaxial bore of the intermediate plate as well as between the side washer and the cover, and the intermediate plate comprises on the periphery of its coaxial bore, a circular segment-shaped recess into which the guide groove opens and whose radially extending end surfaces are configured respectively as a retard and an advance stop. Since the intermediate plate is made of a wear-resistant material, its stops and the guide groove are also wear-resistant.
According to still another advantageous feature of the invention, a peg is arranged on the outer periphery of the disc-shaped bushing and comprises a first and a second radially extending side surface serving as stop surfaces, said peg being pivotable in the circular segment-shaped recess of the intermediate plate between its retard and advance stops. Since the disc-shaped bushing is made of a wear resistant material, the stop surfaces of the peg are also wear-resistant.
The important thing is that, depending on the position of the guide groove in one of the two stop positions of the peg, the locking body can be pushed by a locking spring into the circular segment-shaped recess at an acute angle &agr; to one of the radially extending side surfaces of the peg till a pressure contact acting in peripheral direction is established between a preferably radially extending pressure contact surface of the locking body and one of the radially extending side surfaces of the peg. With an appropriate position of the radial guide groove, it is possible to lock the inner rotor on the advance stop (outlet camshaft) or on the retard stop (inlet camshaft). That radially extending side surface of the peg that is not in abutment with the stop serves in each case as a counter surface of the locking body when it is in the locking position. The locking body is pushed by the locking spring toward the center till the rotational lash becomes equal to zero. The adjustment of the rotational lash required during the assembly of the rotary piston adjuster for reducing noise can thus be dispensed with in the locking device of the invention. The device is even self-locking i.e., an enlargement of the rotational lash due to wear is compensated for by an inward displacement of the locking body by the locking spring.
Due to the fact that the locking body, by reason of the magnitude of the angle &agr; included between its pressure contact surface and its direction of displacement is situated at the borderline of self-locking (quasi self-locking), an unlocking of the locking body under the influence of torque as well as a non-releasable clamping are prevented. This means that the rotary piston adjuster has a high operational reliability.
In an advantageous embodiment of the invention, the spring-distal end of the locking body is in fluid communication with the working chamber A, and its spring-proximate end is preferably in fluid communication with the working chamber B. In the case of an inlet camshaft that is generally locked in the retard position, the rotary piston adjuster bears, at least temporarily, against the retard stop under the influence of the frictional torque of the camshaft when the engine is started. The oil pressure required in the working chamber A for overcoming the frictional torque is then also sufficient for a clamp-free unlocking of the locking body.
Conditions are different in the case of an outlet camshaft whose rotary piston a
Schafer Jens
Steigerwald Martin
Chang Ching
Denion Thomas
Ina-Schaeffler KG
Muserlian Lucas and Mercanti
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