Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-09-26
2002-01-15
Walberg, Teresa (Department: 3742)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090150, C123S090310
Reexamination Certificate
active
06338323
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a vane type variable valve timing control apparatus and control method for changing valve timing of an internal combustion engine.
(2) Related Art of the Invention
As a vane type variable valve timing control apparatus, there is one heretofore disclosed in Japanese Unexamined Patent Publication Nos. 10-141022 and 10-068306.
With this apparatus, recess portions are formed on an inner peripheral face of a cylindrical housing secured to a cam sprocket, while vanes secured to a cam shaft are accommodated in the recess portions, the construction being such that the cam shaft can rotate relatively with respect to the cam sprocket, within a range in which the vanes can move inside the recess portions.
Furthermore, the construction is such that by supplying and discharging oil by means of a spool valve, relatively with respect to a pair of hydraulic chambers (advance angle side hydraulic chamber and delay angle side hydraulic chamber) formed by the vanes partitioning the recess portions into front and rear in the rotation direction, the position of the vanes in the recess portions is changed, thereby enabling a rotation phase of the cam shaft relative to a crank shaft to be continuously changed.
A control value of the spool valve is determined by adding a feedback correction value set depending on a deviation of an actual rotation phase from a target value, to a neutral control value for retaining a rotation phase. A dither signal is then superimposed on the determined control value which is then output to an actuator of the spool valve.
However, as disclosed in Japanese Unexamined Patent Publication No. 10068306, in the case where a resilient body such as a spiral spring for urging the vane to the advance angle side or to the delay angle side is provided, then with a conventional construction in which the neutral control value is constant regardless of a target rotation phase, there is a problem in that the pressure balance cannot be maintained, and a steady-state deviation occurs.
That is to say, with a construction having a resilient body for urging the vane, the urging force of the resilient body varies due to the rotation phase. Therefore, when the valve is driven about the valve position corresponding to the neutral control value, using a constant neutral control value regardless of the rotation phase, the rotation phase is shifted to the advance angle side or to the delay angle side, depending on whether the neutral control value is higher or lower than a suitable urging force. When the rotation phase is shifted from a target, it is then corrected by feedback correction. However, time is required for convergence, and since the correction value requirement differs for each rotation phase, convergence is not possible, causing a problem due to the occurrence of steady-state deviation.
SUMMARY OF THE INVENTION
In view of the above problems it is an object of the present invention, with a vane type variable valve timing control apparatus comprising a resilient body for urging a vane to an advance angle side or to a delay angle side with respect to a cam sprocket, to enable a target rotation phase to be precisely maintained without causing a steady-state deviation.
To achieve the above object, the present invention is constructed such that a neutral control value of a spool valve is set in accordance with a target rotation phase.
With such a construction, a reference position of the valve at the time of retaining the rotation phase is set in accordance with a target value of the rotation phase, to thereby cause the valve to be driven about the valve position corresponding to the target value. As a result, it is possible to supply and discharge oil to each hydraulic chamber at a balance corresponding to the urging force of the resilient body, enabling suppression of the occurrence of steady-state deviation.
Here, the neutral control value of the spool valve is preferably changed according to the oil pressure, as well as being changed according to the target rotation phase.
With such a construction, there is the effect that it is possible to correspond to differences in requirements of the neutral control value due to changes in the oil pressure, and that the occurrence of steady-state deviation due to changes in the oil pressure can be avoided.
Moreover, in the case of a construction where an oil pump for supplying oil to the spool valve is driven by an engine, the rotation speed of the pump is proportional to the rotation speed of the engine, and the oil pressure can be estimated from the rotation speed of the engine. Hence the rotation speed of the engine can be used as a parameter corresponding to the oil pressure.
Furthermore, it is preferable to correct the neutral control value in accordance with the oil temperature.
With such a construction, the neutral control value set in accordance with the target rotation phase is corrected in accordance with the oil temperature, that is, the viscosity of the hydraulic fluid, giving an effect that the occurrence of steady-state deviation due to a change in the oil temperature can be avoided.
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patent: 6006708 (1999-12-01), Ken et al.
patent: 6129060 (2000-10-01), Koda
patent: 6129062 (2000-10-01), Koda
patent: 6135077 (2000-10-01), Moriya et al.
patent: 6186104 (2001-02-01), Torii et al.
patent: 6202610 (2001-03-01), Yoshiki et al.
patent: 6216655 (2001-04-01), Yoshiki et al.
patent: 6230675 (2001-05-01), Kobayashi et al.
patent: 6260526 (2001-07-01), Kobayashi
patent: 10-68306 (1998-03-01), None
patent: 10-141022 (1998-05-01), None
Dahbour Fadi H.
Sughrue & Mion, PLLC
Unisia Jecs Corporation
Walberg Teresa
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