Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2001-02-26
2002-06-18
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090150, C123S090170
Reexamination Certificate
active
06405697
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Application No. 2000-065449 filed on Mar. 9, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to methods and a valve characteristic control apparatus of an internal combustion engine for variably controlling the valve characteristic of an engine valve in accordance with the operation state of the engine.
2. Description of the Related Art
As a valve characteristic control apparatus, an apparatus described in Japanese Patent Application Laid-Open No. 8-177434, as for example, is known. This apparatus includes a valve lift-varying mechanism that allows variation of the amount of valve lift of an engine valve, and a valve timing-varying mechanism that allows variation of the valve timing. If either one of the varying mechanisms has a fault, the following control is performed. That is, with regard to the valve lift-varying mechanism, the mechanism is switched to a low speed type cam. With regard to the valve timing-varying mechanism, a control is performed such that the relative rotation phase of a camshaft is shifted to retarded side. For this control, the presence or absence of a fault of the valve lift-varying mechanism is diagnosed by detecting the hydraulic pressure of hydraulic oil needed for the switching of a cam (low speed type cam, and a high speed type cam) of the mechanism. The presence or absence of a fault of the valve timing-varying mechanism is diagnosed by detecting the rotation phase of a cam (camshaft).
However, as a valve lift-varying mechanism as described above, a mechanism has recently been proposed in which the camshaft is displaceable in the directions of an axis of the camshaft, and in which the camshaft is provided with a generally termed three-dimensional cam, that is, a cam whose cam lobe is continuously varied from one end to the other end thereof in the directions of the axis. According to such a three-dimensional cam type valve lift-varying mechanism, it becomes possible to continuously change the amount of lift of the valve in accordance with the operation state of the engine.
However, in such a three-dimensional cam type valve lift-varying mechanism, the variable control itself is not binary, and is performed with continuous values. Therefore, for the diagnosis regarding the presence/absence of a failure of the mechanism, the diagnostic technique employed by the aforementioned apparatus cannot be simply applied.
Furthermore, technologies have recently been proposed which more suitably maintain the engine characteristic of the internal combustion engine by constructing a valve characteristic control apparatus through a combination of three-dimensional cam type valve lift-varying mechanism and a valve timing-varying mechanism as described above. In the valve characteristic control apparatuses constructed by combining a valve lift-varying mechanism and a valve timing-varying mechanism, the following problems are unignorable with regard to the fault diagnosis.
That is, for example, in a valve characteristic control apparatus employing a cam angle sensor, the fault diagnosis regarding the valve timing-varying mechanism becomes difficult in a relatively early period as the camshaft is displaced by the valve lift-varying mechanism. Furthermore, since both mechanisms use continuous values for their respective variable controls, it is not easy to identify which one of the mechanisms has an abnormality if any abnormality occurs.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide methods and a valve characteristic control apparatus of an internal combustion engine that are capable of precisely diagnosing whether there is an abnormality even with regard to a three-dimensional cam type valve lift-varying mechanism.
In accordance with a first aspect of the invention, a valve characteristic control apparatus of an internal combustion engine includes a camshaft provided with a three-dimensional cam having a cam profile that continuously changes in a direction of an axis of the cam, a valve lift-varying mechanism that allows an amount of valve lift of an engine valve to be varied in accordance with a displaced position of the camshaft in the direction of the axis of the cam, a sensor for detecting valve lift and a controller that receives a signal from the sensor and diagnoses that there is an abnormality of the valve lift-varying mechanism, provided that a deviation between an actually detected amount of valve lift and a target amount of valve lift of the engine valve is greater than a predetermined value and that an amount of change in the actually detected amount of valve lift is less than a predetermined value.
According to the above-described valve lift-varying mechanism, the valve characteristic of the engine valve can be suitably variably controlled by continuously displacing the camshaft provided with the three-dimensional cam in the direction of the axis thereof. However, with regard to the continuous displacement control of the camshaft in the direction of the axis, the target amount of valve lift and the actually detected amount of valve lift are not always equal, due to a response delay in the control.
In this respect, according to the above-described construction, it becomes possible to precisely diagnose that there is an abnormality, that is, an operation abnormality of the valve lift-varying mechanism, based on a determination that the amount of change in the actually detected amount of valve lift is less than the predetermined value even though there is a great deviation between the target amount of valve lift and the actually detected amount of valve lift. In other words, the abnormality is based on a determination that the valve lift characteristic is not in the course of changing.
In accordance with a second aspect of the invention, a valve characteristic control apparatus of an internal combustion engine includes a camshaft provided with a three-dimensional cam having a cam profile that continuously changes in a direction of an axis of the cam, a valve lift-varying mechanism that allows an amount of valve lift of an engine valve to be varied in accordance with a displaced position of the camshaft in the direction of the axis of the cam, at least one sensor that detects actual valve lift and a controller that receives a signal from the at least one sensor and diagnoses that there is an abnormality of the valve lift-varying mechanism, provided that an amount of change in actually detected amount of valve lift of the engine valve is greater than a predetermined value although a state where an instruction to retain the amount of valve lift is outputted has continued for a predetermined duration.
During the state where the instruction is outputted to retain the valve characteristic for a predetermined duration, the amount of change in the actually detected amount of valve lift is considered to become “0” if the valve lift-varying mechanism is normally operating. In this respect, according to the above-described construction, it becomes possible to precisely determine that there is an abnormality, that is, a retainment control abnormality, provided that the amount of change in the amount of valve lift actually detected during that state is greater than the predetermined value.
In accordance with a third aspect of the invention, a valve characteristic control apparatus of an internal combustion engine includes a camshaft provided with a three-dimensional cam having a cam profile that continuously changes in a direction of an axis of the cam, a valve lift-varying mechanism that allows an amount of valve lift of an engine valve to be varied in accordance with a displaced position of the camshaft in the direction of the axis of the cam, a sensor that detects an actual amount of valve lift and a controller that receives a signal from the sensor and diagnoses that there is an abnormality of the valve lift-varying mechanism, provided tha
Denion Thomas
O'Brien Sean D.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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