Apparatus for angular adjustment of camshafts relative to...

Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing

Reexamination Certificate

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Details

C123S090150, C123S090330, C123S1960CP, C123S1960CP

Reexamination Certificate

active

06234125

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to improvements in apparatus for adjusting the camshafts of internal combustion engines.
The purpose of a camshaft adjusting apparatus is to ensure an optimal variable valve control. This is accomplished by ensuring that the valve control phase angle can be adjusted continuously and in an accurately controlled manner. As a rule, such apparatus employ adjusters which are force-lockingly connected with and share the angular movements of the camshafts. An electronic control system is provided to transmit signals which initiate rotary movements of the camshaft. The signals which the control system transmits initiate a preliminary adjustment of the camshaft relative to the crankshaft of the combustion engine.
As a rule, a conventional camshaft adjuster receives motion from a hydraulic drive. The fluid is or can be oil, and the requisite oil pressure is generated by the circuit which serves to pressurize the lubricant for the combustion engine. A drawback of such procedure is that, during the engine start-up phase (this phase is critical as far as the generation of exhaust gases is concerned), the angular position of the camshaft relative to the crankshaft still departs from the desired or optimal position. The reason is that, at such time or stage, the lubricating system is yet to build up a fluid pressure which is necessary to ensure a satisfactory phase adjustment of the camshaft relative to the crankshaft. In other words, the hydraulic drive for the camshaft adjuster is yet to build up the necessary fluid pressure, i.e., the first or initial ignition of the engine takes place prior to accurate phase adjustment of the camshaft relative to the crankshaft. An undesirable side effect of such drawbacks of conventional apparatus is that the rotating camshaft at first turns the idling camshaft adjuster which entails the generation of noise that is readily perceivable by the operator and/or other occupant(s) of the motor vehicle.
OBJECTS OF THE INVENTION
An object of the invention is to provide an apparatus which is constructed and assembled and can operate in such a way that it can carry out all necessary phase adjustments of the camshaft not only after but also prior to initial or first ignition of the combustion engine.
Another object of the invention is to provide an apparatus which operates with a pressurized hydraulic fluid and is constructed and designed in such a way that the required fluid pressure is available prior to initial ignition of the combustion engine, i.e., before the engine lubricating system is capable of supplying a hydraulic fluid at the required pressure.
A further object of the invention is to provide an apparatus which can receive hydraulic fluid at a required or desired or necessary pressure before the lubricating system of the combustion engine is capable of furnishing fluid at a required pressure, and which can receive hydraulic fluid at a requisite pressure from an available source of pressurized fluid, i.e., from a source which need not be provided for the sole purpose of ensuring that the apparatus can carry out the required phase adjustments of the camshaft prior to initial ignition of the combustion engine.
An additional object of the invention is to provide a novel and improved pressure converter for use in the above outlined apparatus.
Still another object of the invention is to provide a novel and improved method of adjusting the camshaft relative to the crankshaft in an internal combustion engine.
A further object of the invention is to provide a novel and improved system of valves for use in the above outlined apparatus.
SUMMARY OF THE INVENTION
The invention is embodied in an apparatus for adjusting the phase of a camshaft in a combustion engine which forms part of a power train in a motor vehicle and has idle and operative (i.e., fired and non-ignited) conditions. The apparatus comprises an adjuster which is operatively (e.g., force-lockingly) connected with the camshaft and is operable to adjust the phase of the camshaft, and drive means for the adjuster. The drive means is arranged to operate the adjuster while the engine is in the idle condition (and, of course, also when the engine is in the operative condition).
The apparatus can further comprise signal generating means which is arranged to monitor actual values of a variable parameter (such as the RPM) of the engine and is connected with the drive means, particularly to control the operation of one or more valves in the drive means. This is particularly important when the drive means is a fluid-operated drive means, e.g., a drive means operated by compressed oil. Such drive means comprises a fluid pressurizing (first) circuit which is arranged to build up a fluid pressure that is necessary for camshaft adjustment by the adjuster while the engine assumes its idle condition.
In accordance with an advantageous feature of the invention, the first circuit forms part of the power steering unit of the motor vehicle.
The engine comprises a second fluid pressurizing circuit (this second circuit preferably serves to lubricate the cylinder head, the engine block and/or other parts of the engine) which is connected or connectable to the drive means for the adjuster. The apparatus preferably further comprises means for connecting the first circuit with the adjuster only during predetermined stages of operation of the motor vehicle (particularly when the engine is idle). Such connecting means can comprise a valve (e.g., a four/three-way proportional valve) which is operable to connect the first circuit with the second circuit. This valve is further connected or connectable with the aforementioned engine RPM sensor or monitoring means so that the latter can ensure the establishment of an operative connection between the adjuster and the second and/or first circuit in the idle condition of the engine.
The apparatus preferably further comprises means for establishing a path for the flow of fluid between the first and second circuits, and means (such as a check valve or a membrane) for regulating the flow of fluid along such path, preferably in such a way that the fluid can flow only from the second circuit to the first circuit.
The regulating means can further comprise a pressure converter which is operable to connect the first circuit with the adjuster for the camshaft of the engine. In accordance with an advantageous feature of the invention, the pressure converter can comprise means (such as a prestressed coil spring) for maintaining the pressure of fluid in the first circuit above a predetermined threshold value which is necessary to ensure that the adjuster can change the phase of the camshaft while the engine is idle.
A presently preferred pressure converter can comprise a housing (e.g., in the form of a cylinder) which defines a high-pressure chamber and a low-pressure chamber, and a piston which is reciprocable in the housing between the two chambers. The first circuit is connected or connectable with the high-pressure chamber, and the second circuit is connected or connectable with the low-pressure chamber.
The drive means can further comprise a valve (such as a four/three-way proportional valve) including a valving element which is movable to a predetermined position in which the first circuit can supply pressurized fluid into the high-pressure chamber of the torque converter.
The aforementioned coil spring or other suitable biasing means can be installed in the higher-pressure chamber to bias the piston (the latter than constitute a twin piston) in a direction to expel fluid from one of the chambers, particularly from the lower-pressure chamber.
The pressure converter can further comprise a deformable bladder or another suitable deformable receptacle which can be installed in the high-pressure chamber to receive pressurized fluid from the first circuit and to seal the two circuits (i.e., the two chambers) from each other.
The first circuit can comprise a fluid reservoir (e.g., a sump which supplies fluid to a pump of the first circuit) and a con

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