Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1994-02-28
1995-06-06
Ryznic, John E.
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
91417R, F01L 134, F15B 1517
Patent
active
054212944
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a hydraulic setting device of the generic type of the main claim. A hydraulic setting device of this type is known from the German Offenlegungsschrift 40 37 834 in which the part pressures in the pressure spaces of a differential cylinder can be varied by means of an electromagnetically actuated control valve. The part pressures in the pressure spaces are set by partial spilling of pressure medium and these part pressures are kept approximately constant by appropriate activation of the control valve. When the differential piston is in a non-transient position, the control valve is activated in such a way that the retention pressures are very much less than the adjusting pressures necessary for an adjusting motion. For this purpose, the annular surface of the differential cylinder is continually subjected to pressure medium by a pump whereas the pressure in the pressure space on the large piston surface can be varied by the electromagnetically actuated control valve. For this purpose, the control valve is configured as a 3/2-way valve and is inserted in a conduit connection between the pump and the pressure space on the large piston surface. Such a hydraulic setting device is employed, for example, in order to actuate a device for adjusting the camshaft relative to the crankshaft (German Offenlegungsschrift 36 16 234) in an internal combustion engine. In order to seal the respective pressure-carrying connection securely against the return connection in the end positions of the control valve, valve element guide gaps--which are sometimes narrow and long--are necessary in these control valves. In consequence, these control valves are sensitive to dirt under certain circumstances, i.e. the valve function can be impaired in the case of dirty pressure medium (engine oil of the internal combustion engine).
ADVANTANGES OF THE INVENTION
The hydraulic setting device according to the invention with the characterizing features of the main claim has, in contrast, the advantage that it operates with low losses when no adjusting motion of the differential piston takes place, that it is of simple construction and that the control valve's sensitivity to dirt is slight.
Further advantages of the invention and advantageous further developments are given in the subclaims and the description.
DRAWING
Two embodiment examples of the invention are explained in more detail in the following description and drawing. The latter shows one embodiment example of a hydraulic setting device in each of FIGS. 1 and 2 in a simplified representation.
DESCRIPTION OF THE EMBODIMENT EXAMPLES
A hydraulic setting device, which has a differential cylinder 11 with a differential piston 12, 13, is indicated by 10 in FIG. 1. The pressure space 14 at the annular surface of the differential cylinder is continually subjected to pressure, via a pressure conduit 15, by a pump 16 which is driven by a drive shaft 17, of the camshaft of an internal combustion engine, for example.
The pressure space 18 on the larger effective piston surface of the differential cylinder is connected, via a conduit 19, to the input 20 of a pressure limiting valve (control valve) 21. The latter has a pressure space 23 configured in a valve housing 22, which is only indicated. A valve element 24, which interacts with a valve seat 25 on the inlet 20, is arranged in the pressure space 23. The pressure space 23 of the pressure limiting valve 21 is connected to a container 27 via a return conduit 26.
The pressure space 23 becomes a longitudinal hole 29 at its end located opposite to the valve seat 25 and this longitudinal hole 29 is closed by the housing 30 of a proportional magnet 31. Two annular control grooves 32, 33 extend, at a distance apart, around the longitudinal hole 29. A control spool 34 is arranged within the longitudinal hole 29 and this control spool 34 has, in its central region, an encircling annular groove 35 which interacts with the control grooves 32, 33 in a manner still to be explained. The actuating push-rod 37 of th
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Leutner Volkmar
Mueller Martin
Pfuhl Berthold
Rembold Helmut
Ruoff Manfred
Robert & Bosch GmbH
Ryznic John E.
Striker Michael J.
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