Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-10-04
2002-06-11
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090160, C123S090170
Reexamination Certificate
active
06401675
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a variable valve operating system equipped with a first variable mechanism capable of controlling lift characteristics of an engine valve such as an intake valve or an exhaust valve, and a second variable mechanism capable of controlling a valve-open and/or valve-close timing.
BACKGROUND ART
As is generally known, there have been proposed and developed various variable valve operating systems that can enhance an engine operating performance by enhancing a degree of freedom of valve operating characteristics by way of a combination of a variable lift mechanism capable of variably adjusting a valve lift characteristic of an intake valve and a variable valve timing mechanism capable of variably adjusting valve-open and/or valve-close timing characteristics.
However, in such conventional variable valve operating systems, there were insufficient studies of a measure to counter in case at least one of the variable lift mechanism and the variable valve timing mechanism fails with an internal combustion engine in operation, thereby causing several problems, that is, mechanical problems such as the interference between at least two of a piston, an intake valve, and an exhaust valve, in particular a problem of remarkably reduced engine performance.
That is to say, in variable valve operating systems disclosed in Japanese Patent Provisional Publication No. 4-287809 and Japanese Utility Model Provisional Publication No. 3-99860, a variable lift mechanism and a variable valve timing mechanism both use hydraulic pressure as an energy, source. Therefore, in presence of a hydraulic system failure, for example, in presence of a failure in an electromagnetic switching valve disposed in the middle of a hydraulic circuit or in presence of a failure in a hydraulic equipment included in a hydraulic pressure control system, a malfunction of the variable lift mechanism and a malfunction of the variable valve timing mechanism occur. In this case, it is difficult to variably control both of avalve lift and avalve timing. As a result of this, it is impossible to produce a sufficient engine performance, and also there is a possibility of remarkably reduced engine performance due to particular engine operating conditions.
Additionally, even when a hydraulic system failure does not occur, owing to a high viscosity resistance at low oil temperature conditions such as during an engine start-up period, it is difficult to insure a satisfactory operation of each of the variable lift mechanism and the variable valve timing mechanism. Due to the high viscosity resistance as well as a long length of a hydraulic pressure passage, a delay in hydraulic pressure supply from a hydraulic pump to each of the variable lift mechanism and the variable valve timing mechanism occurs. Owing to such a system malfunction, there is a technical problem of a reduced control response for each of the variable lift mechanism and the variable valve timing mechanism to a change in the engine operating condition for a while after starting.
As an additional prior art, Japanese Patent Provisional Publication No. 8-177434 also discloses a variable valve operating system.
Roughly speaking, the previously-noted variable valve operating system is equipped with a valve lift control mechanism capable of variably controlling a cam lift of an intake valve (serving as an engine valve) or a cam lift of an exhaust valve (serving as an engine valve) by selectively switching from one of a low-speed cam and a high-speed cam (both provided on a camshaft) to the other depending on engine operating conditions, and a valve timing control mechanism capable of variably controlling a valve-open and/or valve-close timing by changing a relative angular phase between the camshaft and a crankshaft depending on the engine operating conditions.
Additionally, the above-mentioned system is also equipped with a control mechanism provided to avoid the interference between the intake valve and the exhaust valve by forcibly switching to the low-speed cam by means of the valve-lift control mechanism in presence of a failure in the previously-noted valve timing control mechanism, or by controlling the valve-open and/or valve-close timing of the engine valve by means of the valve timing control mechanism so that a center of operation of a valve lift moves away from a top dead center in presence of a failure in the previously-noted valve lift control mechanism.
In the aforementioned variable valve operating system, as discussed above, it is possible to avoid the mechanical problem such as the interference between the intake valve and the exhaust valve in presence of a failure in each of the valve lift control mechanism and the valve timing control mechanism. However, in case either one of the control mechanisms fails, the system functions to forcibly switch to the low-speed cam by means of the valve lift control mechanism or to control a valve-open and/or valve-close timing so that the center of operation of a valve lift moves away from the top dead center by virtue of the valve timing control mechanism. As a matter of course, a valve overlap through which both the intake and exhaust valves are open together becomes reduced. Therefore, in a high engine-speed operating range, the engine power output tends to reduce, and thus it is difficult to produce a satisfactory engine performance.
DISCLOSURE OF THE INVENTION
In order to accomplish the aforementioned and other objects, according to the invention as claimed in claim
1
, a variable valve operating system of an internal combustion engine comprises a first variable mechanism capable of variably controlling at least a lift characteristic of an engine valve depending on an engine operating condition, and a second variable mechanism capable of variably controlling at least a valve-open and/or valve-close timing characteristic of the engine valve depending on the engine operating condition, characterized in that the first variable mechanism is driven by an electric actuator, whereas the second variable mechanism is driven by hydraulic pressure of working fluid, and in that the system inhibits the second variable mechanism from being driven and allows only the first variable mechanism to be driven within an operating range from engine start operation to a time when a temperature of the working fluid reaches a predetermined temperature value, and the system allows both the first and second variable mechanisms to be driven from a time when the temperature of the working fluid exceeds the predetermined temperature value.
In accordance with the previously-noted invention, a power source of the first variable mechanism is different from a power source of the second variable mechanism. Except the engine starting period, even in case either one of an electric system and a hydraulic system fails, the other variable mechanism cannot be affected, and thus at least one variable mechanism can be driven normally. Therefore, it is possible to prevent the engine performance from lowering. Furthermore, during the engine starting period a valve lift is generally adjusted to a small amount, and therefore there is no problem of the previously-discussed interference even in presence of the system failure.
Additionally, even when both the variable mechanisms are driven, actuation of the second variable mechanism, using hydraulic pressure as a power source, is inhibited during the engine starting period, and is allowed from the time when the temperature of working fluid reaches the predetermined temperature value. Thus, for a while from the engine starting, it is possible to enhance various engine performances, such as a startability, owing to high-response lift control of the first variable mechanism. Additionally, after a rise in the temperature of working fluid, it is possible to largely enhance the engine performances by way of a combination of both the first and second variable mechanisms.
According to the invention as claimed in claim
2
, a valve lift of the engine valve is controlled to a minimu
Nakamura Makoto
Okamoto Naoki
Takemura Shinichi
Corrigan Jaimie
Denion Thomas
Foley & Lardner
Unisia Jecs Corporation
LandOfFree
Variable valve gear device of internal combustion engine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Variable valve gear device of internal combustion engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Variable valve gear device of internal combustion engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2956982