Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1989-12-11
1992-11-03
Okonsky, David A.
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
123 9017, 123 9031, 474110, F01L 134
Patent
active
051599040
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for adjusting the angular setting of at least one driven shaft relative to a driving shaft in an internal combustion or explosion engine.
In an internal combustion or explosion engine it is necessary during its operation to ensure a synchronism in particular of the control of the opening and closing of the valves and/or the injection with the movement of the pistons. This synchronism is generally obtained by means of a chain, termed a timing gear chain, which, as it is driven in rotation by a chain wheel rigidly connected to the crankshaft, itself drives either a camshaft ensuring the opening and the closing of the valves, or an element of an injection pump.
A chain tightener ensures the tension of the chain and takes up play due to wear.
It is moreover known that it is of utility to be able to vary the angular setting of the driven shafts relative to the driving shaft as a function of the engine operating condition. Such a variation permits improving the efficiency and reducing pollution due to a discharge of incompletely burnt gases.
The adjustment of the angular setting of the shaft controlling the opening and closing of the valves has been dealt with in the prior art and more particularly in the French patent 2529617 which prescribes for the setting of the distribution and/or the injection, a shaft whose angular position may be adjusted by means of a train of meshed helical gear pinions.
In other devices, the pinion driving the camshaft is constituted by a hub rigidly connected to the camshaft and a ring gear disassociated from the hub and connected to the latter either by a hydraulic coupling or by a planet gear mechanism so as to be capable of achieving an angular offset between this ring gear and the hub connected to the shaft.
These known devices have many drawbacks among which is the complexity which renders them hardly reliable and of high cost. Moreover, they have a large overall size whereas the regions in which they must be located are restricted.
Such devices also have an important drawback, namely of being difficult to control. Indeed, they permit varying the setting of the driven shaft relative to the driving shaft between two end positions without possibility of obtaining intermediate positions.
An object of the present invention is to propose a method for adjusting the angular setting of at least one driven shaft driven in rotation by a driving shaft in an internal combustion engine, which is of simple construction, reliable in operation and consequently overcomes the drawbacks of existing devices.
For this purpose, the invention provides a device for driving at least one driven shaft by means of a driving shaft, comprising a closed-loop transmission connection of constant length defining a slack side on which a first tightener acts and at least one tight side on which a corresponding tightener acts, characterized in that the tighteners are hydraulic tighteners having a valve each including a chamber continuously fed with a control fluid under pressure and provided with bleeder means controlled by a sequential control unit for varying the angular setting of the driven shaft relative to the driving shaft.
Such a device permits obtaining an adjustment of the angular setting in particular of a camshaft relative to a crankshaft in an internal combustion or explosion engine in a simple, reliable and precise manner with a small overall size, since the device is located between the different rotating shafts.
According to other characteristics:
the bleeder means of each tightener comprise an electrically-operated valve EV on the downstream side of an outlet of the chamber and a variable throttle R located on the downstream side of the electrically-operated valve and on the upstream side of a bleeder reservoir.
the control unit comprises an inlet connected to sensors of parameters of operation of the engine, a microprocessor and an outlet delivering control signals to the bleeder means.
the control unit sends in a sequential manner control signals to the b
REFERENCES:
patent: 3888217 (1975-06-01), Hisserich
patent: 4478595 (1984-10-01), Hayakawa et al.
patent: 4533341 (1985-08-01), Yokota
patent: 4715333 (1987-12-01), Oyaizu
patent: 4850941 (1989-07-01), Sosson
Lo Weilun
Okonsky David A.
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