Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reissue Patent
2000-02-02
2001-07-10
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090310, C123S090330, C123S1960AB, C123S19800E
Reissue Patent
active
RE037268
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device disposed on an internal combustion piston engine for changing rotational relations between at least one camshaft and a crankshaft, with the device being provided with a hydraulic cylinder which is acted upon by hydraulic fluid by means of a supply unit driven by the internal combustion piston engine.
BACKGROUND OF THE INVENTION
A device of this type is known for example from WO-A 93 07 362. Linear adjusting movements of the hydraulic cylinder are converted by way of an actuator into a relative rotation of the camshaft in respect to the crankshaft. Such an actuator can be positioned between a pinion and the camshaft with the pinion being driven by the crankshaft via a traction means. The actuator which is placed coaxially with respect to the pinion and the camshaft can be provided with a helical teeth or with a straight teeth, whereby these teeth cooperate with mating teeth associated with the camshaft and the pinion. When the hydraulic cylinder is operated, the actuator is axially displaced in relation to the pinion and the camshaft, whereby the helical teeth cause the camshaft to rotate relative to the pinion and thereby also relative to the crankshaft. An oil pump is driven by the camshaft of the internal combustion engine in a manner known in the art. In these conventional devices, the motor oil is empoyed as a hydraulic fluid for acting on the hydraulic cylinder. When the engine stops, the pressure in the hydraulic cylinder decreases to zero and motor oil leaks out of the hydraulic cylinder. During start of the engine, the oil pump is not yet capable of building up pressure. In the event the engine is started after it was shut down for an extended period of time, motor oil stored in the cylinder will have leaked out to such an extent that compressible gas cushions are formed in the cylinder. Consequently, the piston is able to move linearly inside the pressure chambers even if the pressure chambers are sealed off. The alternating torque transmitted by the camshaft to the actuator exerts axial forces onto the actuator caused by the described helical teeth. These axial forees cause undesirable oscillatory movements of the actuator as a consequence of the compressible gas cushions.
It is thus an object of the present invention to reliably eliminate these undesirable movements of the actuator.
SUMMARY OF THE INVENTION
This object is solved in accordance with the invention by displacing gas cushions encountered in the hydraulic cylinder by means of the supply unit immediately before and/or during the starting operation of the internal combustion piston engine and replacing these gas cushions with hydraulic fluid, in particular motor oil. This supply unit is activated before the engine is started, for example, during ignition or during preheating the motor. Alternatively, the supply unit according to the invention can also be activated during rotation of the starter of the motor. Of course, there could also be provided a circuit for operating the supply unit when the ignition is started and the starter turns. A supply unit of this type can, for example, be formed by a second oil pump driven by an electromotor which is provided in addition to the conventional first oil pump that is driven by the internal combustion piston engine. This elctromotor is preferably operated by the battery provided in the motor vehicle. This second oil pump can be located directly in a pump well of the oil pan, but also in the cylinder head. Depending on the location of the second oil pump, there can be provided an oil reservoir separate from the oil pan from which reservoir the second oil pump draws. In particular at low temperatures, it may be suitable that motor oil preheated in a preheater is then transported to the hydraulic cylinder by the second oil pump. This preheater may, for example, be located in the separate oil reservoir. This preheater can also be operated by the car battery in a same manner as the second oil pump. A heat reservoir can also be employed instead of or together with the prebeater. Since in particular the automobile industry now requires increasingly assembled subsystems, it is suitable to form the separate oil reservoir, the second oil pump, the electromotor and the preheater as a structural unit. This structural unit can then simply be flange-mounted on the engine.
It is also feasible to provide the supply unit in the form of an oil pump which can be driven by the internal combustion piston engine as well as by an electromotor, with a coupling unit being provided for selectively coupling the oil pump to the electromotor or to the internal combustion piston engine. This can be implemented, for example, by using two conventional freewheel clutches, with one of the clutches being connected between the oil pump and the crankshaft and the other clutch being connected between the oil pump and the electromotor.
In order to ensure that the separate oil reservoir is continuously filled with motor oil, a return line is proposed which leads into the separate oil reservoir. Excess motor oil is thereby returned to the oil pan and the oil reservoir, so that motor oil is again transported from the filled oil reservoir to the hydraulic cylinder when the ignition is started the next time.
The supply unit, however, can also be implemented in form of a hydraulic accumulator. The liquid stored in this device is under pressure by a spring, a gas or a weight. The stored energy is released again in form of a liquid flow under pressure. Suitably, a disengageable check valve may for example be so arranged between the hydraulic accumulator and the hydraulic cylinder that the motor oil can flow from the hydraulic accumulator into the cylinder upon ignition and released check valve.
It is suitable, to connect a disengageable check valve between between the hydraulic accumulator and the hydraulic cylinder, with the check valve being releasable by an electromagnet and closing in the direction of the hydraulic cylinder. The electromagnet can, for example, be actuated simultaneously with the ignition. Before the engine starts, motor oil is pumped into the hydraulic cylinder through the open check valve, thereby displacing existing gas cushions.
REFERENCES:
patent: 4890695 (1990-01-01), Morris et al.
patent: 4940114 (1990-07-01), Albrecht
patent: 5170755 (1992-12-01), Kano et al.
patent: 5189999 (1993-03-01), Thoma
patent: 5195474 (1993-03-01), Urata et al.
patent: 5243935 (1993-09-01), Kano et al.
patent: 5247914 (1993-09-01), Imai et al.
patent: 5329890 (1994-07-01), Mueller
patent: 5509383 (1996-04-01), Kahrs et al.
patent: 5615648 (1997-04-01), Ruoff et al.
patent: 5704317 (1998-01-01), Barth
patent: 39 29 078 (1991-03-01), None
patent: 42 27 001 (1994-02-01), None
Patent Abstracts of Japan vol. 16, No. 578 (M-1346), Dec. 17, 1992 & JP 04 228815 A (Honda Motor Co. Ltd.), Aug. 18, 1992, see abstract.
Scheidt Martin
Strauss Andreas
Feiereisen Henry M.
Ina Walzlager Schaeffler OHG
Lo Weilun
LandOfFree
Adjusting cylinder of a camshaft adjusting device acted upon... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Adjusting cylinder of a camshaft adjusting device acted upon..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Adjusting cylinder of a camshaft adjusting device acted upon... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2479596